This Tokay gecko (scientific name Tokay tokay) is opening its mouth in defence as it feels threatened.
Tokay geckos are one of the more aggressive geckos, often known as the bulldog of geckos
. Its rare that you can approach them without the gaping like this , both as a defence and to scare of predators. The frequently bite, so dont make for the best pet if you want to handle your lizard. They are skittish and move extremely fast, so are more suited as a pet that you observe rather than handle.